The present invention relates to liquid delivery systems for processing chambers. More particularly, the invention relates to an apparatus and method for purging a processing liquid from a liquid delivery system using ultrasonic energy.
Many semiconductor processes such as chemical vapor deposition (CVD) employ liquid delivery systems to supply reactive precursors to chambers for processing. Liquids are typically vaporized and supplied to a processing chamber via a liquid delivery system comprising an interconnecting network of pipes, isolation valves, flow regulators and vaporizing mechanisms. Over time, the components of the liquid delivery system may require replacement due to mechanical failure or require cleaning due to deposit formation within the liquid delivery system. However, replacing a component of the liquid delivery system such as a vaporizing mechanism is a complicated and slow process. Additionally, many processing liquids, such as metal organic precursors for CVD processes, are difficult to remove from the surfaces of the lines and the cracks and crevices formed by the mechanical components of the liquid delivery system. These difficult to remove processing fluids may remain as liquid residue during the process of replacing components.
During system maintenance including component replacement process, the liquid residue in the liquid delivery system and/or components therein may react with oxygen and moisture in the ambient air to form undesirable by-products. These by-products are often solid films such as oxides that may damage the liquid delivery system or may pose a particle problem during subsequent deposition processes. When oxide particles contaminate a deposition process, the subsequently formed films may peel from the adjacent layers or substrate, and if the contamination is severe enough, may render the substrate unusable.
To prevent contaminants from forming during the replacement of components in the liquid delivery system, the processing liquid is purged from all processing liquid paths that will be exposed to the atmosphere when the component is removed. Typically, an inert purge gas, such as nitrogen, is used to remove the undesirable residual processing liquid. However, purge gases are only moderately effective at removing most residual processing liquids and are even less effective at removing particulate matter lodged within the components of the system. The gas purge process is typically ineffective for removing processing liquids that readily adhere to the components and lines of the liquid delivery system and often requires a substantial volume of purge gas to completely sweep out the residual processing liquid.
One approach to improving the effectiveness of the purge process is to employ a xe2x80x9cflushing liquidxe2x80x9d to reduce the retention of the processing liquids in the liquid delivery system. Flushing or purge liquids are often solvents for the processing liquids. For instance, one example of a metal organic precursor used as a processing liquid in chemical vapor deposition is tetrakis(dimethylamino)titanium (TDMAT). TDMAT is typically used in the deposition of titanium nitride (TiN) layers. A flushing or purge liquid of hexane, a solvent of TDMAT, is typically used to purge TDMAT from a liquid delivery system. Unfortunately, if a processing liquid is particularly difficult to remove, such as TDMAT, the flushing solvent process may still be ineffective at removing all of the residual processing liquid and particulate matter from cracks and crevices formed by the mechanical components of the line. Like the purge gas, the flushing liquid solvent process typically requires a substantial volume of purge liquid to completely sweep out the processing liquid.
One hardware solution to minimize processing liquid contamination during liquid delivery system component removal is to limit the amount of the system exposed to potential contamination. The hardware solution provides for an isolation valve assembly composed of at least two isolation valves, a pump valve, and a purge fluid valve configured to reduce the exposed line defined by the valves. In the assembly, the two or more isolation valves are closed to isolate the region containing the line and/or corresponding component from the system. Typically, isolated components are those sensitive to contamination or require frequent replacement.
Coupled to the isolated region are a purge valve and a pump valve. The purge valve opens to allow a purge fluid to enter the isolated region and the pump valve is opened to evacuate the residual processing liquid and purge fluid from the isolated region. Once purging is complete, the purge and pump valves are closed and the component may be removed. The valve arrangement allows the isolated component of the system, such as a dysfunctional injection valve, to be more efficiently purged with less purging fluid. However, these systems simply limit particle contamination to smaller portions of the line, and still may not effectively purge processing liquids from the line nor improve the removal of particulate matter from the cracks and crevices of the devices of the liquid delivery system.
Accordingly, there exists a need for a processing liquid purging method and apparatus that more effectively purges processing liquids and contaminates from a processing liquid delivery system without requiring additional expense and complexity associated with the use of processing liquids or purging fluids.
The present invention generally provides an apparatus and method for purging a liquid delivery system used in integrated circuit manufacturing. More particularly, the invention provides a liquid delivery system comprising one or more liquid delivery components defining a processing liquid path, and at least one ultrasonic transducer mounted on the one or more liquid delivery components. A purge fluid, preferably a solvent, is flowed through the liquid delivery system and the ultrasonic transducers launch energy into the purge fluid to improve the purge process.
In one embodiment, the invention provides a liquid delivery system comprising one or more liquid delivery components defining a processing liquid path and an ultrasonic transducer mounted on one or more liquid delivery components. The components of the liquid delivery system may include one or more liquid flow meters, one or more isolation valves, one or more vaporizing elements, one or more fluid lines, and combinations thereof. Further, one or more liquid delivery components may comprise one or more housings with at least one ultrasonic transducer mounted on the one or more housings. In another aspect, one or more liquid delivery components may comprise a gas box comprising a liquid source assembly, a fluid purge assembly, and an isolation valve assembly, and have at least one ultrasonic transducer mounted on the gas box. The liquid delivery system may further comprise a heater in thermal communication with the processing liquid path.
In another aspect, the invention provides a liquid delivery system comprising a plurality of housings, or enclosures, and assemblies disposed along and forming a part of a processing liquid path, which includes a gas box, a direct liquid introduction enclosure coupled to the gas box, a pump valve assembly operatively coupled to the liquid introduction enclosure, and at least one ultrasonic transducer mounted on the gas box, the direct liquid introduction enclosure, the pump valve assembly, or a combination thereof. The liquid delivery system may further comprise a heater in thermal communication with the processing liquid path.
In another aspect, the invention provides a method of purging a liquid delivery system by introducing a purging fluid into the liquid delivery system, launching ultrasonic energy into the purging fluid within the liquid delivery system, and pumping the processing liquid and the purging fluid from the liquid delivery system. These steps may repeated until the liquid delivery system is sufficiently purged of processing liquid. The system may be flushed to remove all residual processing liquid following the purging and pumping steps. The purging and flushing fluid may be a liquid, a gas, or a combinations thereof, but is typically a liquid solvent of the processing liquid. To further improve the removal of contaminants, heat may be applied to the system at a temperature from about 70xc2x0 C. to about 800xc2x0 C. during the purge process to improve the dissolution of contaminants into the purge fluid.